Gravity flow carafe filters have been commercially available for several years and their popularity with consumers continues to grow. Currently available commercial water carafes are capable of removing lead using an ion exchange resin, undesirable tastes and odors using carbon granules, and large particles using a packed bed configuration. However, up to the present time, water carafes of commercially available design have not been capable of parasite reduction, which requires much finer filtration. Nor have they been effective for the complete removal of organic chemicals, pesticides and insecticides, which requires more carbon. While such additional removal attributes are desirable, they have not been technically feasible in the filter sizes required and at the filter cost currently in the market.
The need for additional carafe functionality has been recognized and proposals to add parasite reduction capabilities have been made. A major problem to be solved for carafe applications, however, is that of achieving an adequate filter flow rate. Unlike filter cartridges for in-line or pressurized water filtration systems, cartridges for carafes must operate under water pressures developed by gravity alone. Membranes and other micro-porous filter materials with porosity sufficiently fine to exhibit cyst reduction capability have for the most part been viewed as exhibiting inadequate flow rates for systems other than those using a high-pressure water supply.